The mechanism of the primary interaction between oncornaviruses and host cell surface is unknown. The study will explore the specificity of adsorption between Rous Sarcoma Virus and chicken cell membranes with the aim of developing an in vitro assay for virus adsorption. Preliminary studies in our laboratory have shown that chicken cell membranes will bind Rous Sarcoma Virus more avidly than control (human erythrocyte) membranes. This binding is not dependent upon lithium diiodosalicylate extractable membrane glycoproteins or readily extractable surface proteins. Studies are now in progress to delineate the exact nature of these Rous Sarcoma Virus receptors.